Numerous methods are known during which one operation is the drying of agglomerated raw materials the grains of which show a small mechanical strength prior to their further processing in a process line. This is a situation e.g. in the process of manufacture of aggregates sintered from power plant cinders for the building industry and road building industry. When an aggregate is manufactured by sintering on a sintering belt (e.g. the Lytag technology) freshly granulated raw materials pouring out of a granulating plate are practically directly poured onto a sinter belt, where without any further pouring they are successively dried and sintered. In this way the problem of a drying operation is so to say by-passed. However, if the same process is carried out utilising the energy contained in raw materials (even autothermally) with this process as well being combined with utilisation of post-fermentation sediments, post-refining sediments or other therefore in a shaft oven (e.g. the Wrogran technology) or in a rotary oven (Gralit and LSA technology), then prior to feeding grains to a sintering equipment they should be first dried in order to obtain among other things the mechanical strength required for baking and sintering. In such cases belt dryers are usually used which while ensuring a minimum of pouring-over steps of mechanically weak grains at the same time transport these grains and feed them to an oven. However, the overall dimensions of belt dryers are relatively large, they consist of many moving parts, which wear out quickly, and are difficult to insulate to reduce thermal losses. Additionally, e.g. with the LSA technology, a direct feeding of hot granules from a belt dryer to a rotary concurrent oven would be difficult to realise due to process problems and space requirements.
A column pulse-fluidisation dryer is known from a Polish patent specification No 153746. On its top it comprises a wet material feeding batcher and in its bottom a discharging outlet of dried material and a number of drying sections equipped with an inlet collector with a gas inlet, gas distributors, thrust chambers ending with a screen shelf, a drying chamber equipped with a pour-over threshold and a gas outlet stub pipe. The middle drying sections are interconnected over pour-over channels for the material subject to drying. The drying sections are stacked one upon another, where the lower a given drying section is situated the higher is its pour-over threshold.
A closed loop drier for drying vegetable materials is also known from a Polish patent specification P376869. It has the form of a cylinder with shelves, where this cylinder is divided into a drying and a cooling part. Below an outlet or possibly outlets of hot gas there are mounted two not perforated shelves serving as a lock. The drying part is provided with drying shelves in the form of jalousie-type perforated laths. In the cooling part there are cooling shelves in the form of jalousie-type perforated laths under which there are an inlet stub pipe or inlet stub pipes of cooling gas. An outlet stub pipe or stub pipe outlets of cooling gas are situated above cooling shelves in which outlet or outlets exchangeable filters for the dust of the circulation gas and a dust blower are mounted. A rotary spreader for vegetable material (dried) is situated above the drying shelves and a rotary rake-out is situated under the cooling shelves. A vegetal material charging pipe and the outlet or outlets of the drying gas is mounted in the cover. Under the cover there are a rotary brush and replaceable gas filters for gas carried out from the drier, where further this gas is directed through the filter, cooler and a condensed water separator to the cooling section of the drier under the lowest shelf. The drier bottom is equipped with a stub pipe, preferably a square one to receive the dried vegetal material.